How to wash linen so it gets better
Most fabrics are at their best on the day you buy them and go downhill from there. Linen is the exception. It softens, it settles, and it looks better in its third year than in its first month. Almost nothing you do in a normal wash will hurt it.
Wash it cold, and skip the softener
Cold machine wash, normal cycle, mild detergent. The one thing to leave out is fabric softener. It coats the fibre, and coating the fibre is precisely what stops linen softening on its own. The cloth does that by itself, with every wash, for free.
Wash strong colours on their own for the first two or three washes. Indigo, black and burnt orange carry loose dye at the start.
Dry it in the shade
Line dry out of direct sun. Sun will pull the colour out of a deep shade over a season. If you need the dryer, run it low and take the piece out while it is still slightly damp.
Iron it damp, or not at all
If you want it crisp, iron on the linen setting while the cloth is still damp and press on the reverse. If you do not, leave it. Creases are what linen looks like. A linen dress with no creases in it is usually not linen.
Treat stains cold
Cold and quick. Hot water sets a stain into linen rather than lifting it.
Fold it, do not hang it
Linen is happy in a drawer and does not need a hanger. Unlike wool it does not attract moths. If you are putting something away for a season, wash it first. A mark left sitting in the cloth will darken over time.
About shrinking
Our linen is washed before it is cut, so most of the shrinking has already happened by the time the pattern goes on. Expect a little more in the first wash and very little after.
The point
Linen is not a fabric you protect. It is a fabric you use. The softness people love in old linen is not a finish applied at the mill, it is what happens after fifty washes.